The analog active filter is one of the basic elements of modern audio electronic equipment. The filter's low cost and accuracy make it a preferred choice in many designs. Typically, the final active filter is generated by a cascade connection of many simple active filters and is thus known as a multi-cascade filter. A problem with the multi-cascade filter is that the input signal passes through multiple amplification stages, each stage introducing a degree of signal distortion. In conventional high quality audio systems, the resulting overall signal distortion is considered to be unacceptable.
what is needed is an improved active filter network that exhibits a smaller overall signal distortion than normally present in conventional multi-cascade filters. At the same time, the improved network would maintain the advantages of low cost and accuracy found with conventional networks.